The U.S. women's team of Misty May-Treanor and Kerri Walsh challenge Australia's Nat Cook and Tamsin Hinchley during a beach volleyball event at the Horse Guards Parade and 10 Downing Street, the home of the British prime minister.

U.S. players Carli Lloyd, right, celebrates with teammates Megan Rapinoe, center, and Alex Morgan after scoring their third goal during the Women's Football first round Group G match between against Colombia on Day 1 of the London 2012 Olympic Games.

The United States' Timothy Wang serves against North Korea's Kim Song Nam in a preliminary-round table tennis match. Wang was overwhelmed in his first Olympic appearance, losing in four straight games.

2012 London Olympics | Day 1

Competition in the 2012 Summer Olympics in London is officially underway.

U.S. swimmer Michael Phelps barely qualified in the 400-meter individual medley, squeaking into the final by seven-hundredths of a second.

Spectators cheered as the pack rode by during the men’s road cycling race.

In other action, Natalia Sheppard and Sophie Troiano met in an all-British match in women’s fencing; Felipe Kitadai of Brazil advanced in the men’s 60-kilogram judo competition; and Timothy Wang of the U.S. fell to Kim Song Nam of North Korea in a table tennis preliminary.